Abstract- Index Terms IJSER...tangential injection causes the flow in the chamber to swirl and...

International Journal of Scientific & Engineering Research, Volume 7, Issue 3, March-2016 69 ISSN 2229-5518

IJSER © 2016 http://www.ijser.org

Reduction of Combustion Chamber Heating

by Swirl Shield flow in Liquid Propellant

Rocket Engine Samson PS, Sreemol Balakrishnan, Jerin Cyriac, SarinJose, Rohan Paulose, Leo kJ

Abstract-Ina swirl shield combustion rocket engine theoxidizer is injected tangentially into cylindrical chamber which is

closed at one end and which has a converging outlet at the other end. The flow is introduced into the interior of the

chamber near the outlet end of the chamber and in a direction which is tangent to the inner wall of the chamber. This

tangential injection causes the flow in the chamber to swirl and follow a spiral path up the inner wall of the chamber

and carry away the generating heat due to combustion.

Index Terms-CFD, engine rich exhaust, heat transfer, inner vortex, outer vortex, rocket engine, swirl shield, vertical

helix.

1 INTRODUCTION

THERE are many parts in a rocket, the

Important among them are its payload system,

guidance system, propulsion system, structure

system.The rockets run with combustion

temperatures that can reach ~3500 K (~3227 °C

).Therefore temperatures used in rockets are very

often far higher than the melting point of the

nozzle and combustion chamber

materials(~1200K). Two exceptions are graphite

and tungsten although both are subject to

oxidation if not protected .Here comes the

importance of cooling system in the rocket. If it is

not properly cooled it will be dangerous to the

equipments in it,to the body of the vehicle.so the

temperature should be controlled properly. Indeed

many construction materials can make perfectly

acceptable propellants in their own right. It is

important that these materials be prevented from

Combusting, melting or vaporizing to the point of

failure.

Alternatively, rockets may use more

common construction materials such as

Aluminium, steel, nickel or copper alloys and

employ cooling systems that prevent the

construction material itself becoming too

hot. Regenerative cooling, where the propellant is

passed through tubes around the combustion

chamber or nozzle. Dump cooling (a propellant,

generally hydrogen is passed around the chamber

and dumped), Curtain cooling (propellant injection

is arranged so the temperature of the gases is

cooler at the walls),Film cooling (surfaces are

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wetted with liquid propellant, which cools as it

evaporates).

The object of the present invention is to provide an

improved combustion chamber and method

utilizing the above-described double vortex flow

field. Another object of the present invention is to

provide an improved combustion chamber and

method utilizing the above flow field and to

provide for increased fuel regression rates and

increased travel distance and mixing to achieve

complete combustion. A further object of the

present invention is to provide a liquid rocket

engine utilizing the above-described vortex flow

field. A still further object of the present invention

is to provide an improved hybrid rocket

propulsion system that facilitates and promotes

high and uniform fuel grain regression rates so

that small combustion ports can be used in the

propellant solid grain.

2 WORKING

A liquid rocket engine and a method for

propelling a rocket utilizing a vortex flow field. The

flow field includes an outer fluid vortex spiraling

toward a closed end of the flow field generating

apparatus and an inner fluid vortex substantially

concentric with the outer vortex spiraling away

from the closed end and toward an outlet opening

in which the inner vortex spirals in the same

direction as the outer vortex, but in the opposite

axial direction. The flow field in accordance with

the present invention is capable of providing

separate regions or zones within and among one or

more flowing fluids contained within a common

chamber, without the need for diaphragms or

other physical separators or barriers. Another

embodiment is in the form of liquid rocket engine

to prevent hot combustion products from

contacting the chamber wall.

Virtually countless applications exist for a

flow field Many devices depend upon vortex flows

for their successful operation, such as combustion

chambers, cyclone separators, classifiers and the

like that are in common use. All of these devices

introduce swirling flow at one end of a

passageway in which the flow follows a generally

helical path to exit at the opposite end. Such

conventional vortex flows do not achieve zonal

separation as does the unique flow field that is the

subject of the present invention. it has particular

application to the field of rocket engines and in one

embodiment, specifically to hybrid rocket engines.

Hybrid rocket engines denote a class of rocket

propulsion systems in which one propellant is in

fluid form and the other propellant is in the form

of a solid grain. Typically, the fluid propellant is

the oxidizer and the solid grain is the fuel. The

oxidizer such as liquid oxygen is sprayed into the

combustion ports in the solid fuel grain and caused

to ignite. The hot combustion products sustain the

combustion process until either the oxidizer flow is

shut off or the fuel grain is depleted. The burn rate,

often expressed as regression rate, is the rate at

which fuel can be induced to vaporize the grain

surface so it can participate which provides

separate regions or zones of flowing fluids within a

chamber. There is also a need in the art for a

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combustion chamber and method utilizing such a

flow field, and particularly a combustion chamber

and method for a hybrid rocket engine, which

significantly increases the regression rate of the

solid fuel grain and the effective chamber length

and mixing within the combustion chamber. There

is also a need for a combustion chamber and

method utilizing such a flow field that prevents the

hot combustion products from reaching the

chamber wall.

Figure 1; combustion chamber

In accordance with the present invention, a fluid

flow field, and a structure and method for

producing and sustaining the field, has been

designed. This flow field provides for separate

regions or zones of flowing fluids within a

chamber without the need for physical barriers or

other separators and without substantial mixing

between the regions or zones. In a revolutionary

departure from prior art the present invention

introduces the incoming swirling flow concentric

to the outlet passage and by this means establishes

a new and unique flow field. The flow field

inherently divides into an outer upwardly flowing

vertical helix along a chamber wall, an inner

downward flowing vertical helix along the center

region of the chamber, a converging flow field at

the head end where the outer vortex transforms

into the inner vortex, a converging flow field as the

flow approaches the exit nozzle, and less well

defined regions of velocities and pressure

gradients elsewhere throughout the chamber.

The flow field is produced by injecting

flow tangentially into a cylindrical chamber which

is substantially closed at one end and which has a

converging outlet at the other end. The flow is

introduced into the interior of the chamber near

the outlet end of the chamber and in a direction

which is substantially tangent to the inner wall of

the chamber. This tangential injection causes the

flow in the chamber to swirl and follow a spiral

path up the inner wall of the chamber thereby

establishing an annular vortex flow bounded by

the inner wall of the chamber. When the spiral

flow reaches the closed end of the chamber, the

flow inherently translates inwardly to the center of

the chamber to form the second vortex where the

flow moves spirally away from the closed end,

down the core of the chamber and out the chamber

nozzle. This inner vortex or spiral flow through the

center of the chamber rotates in the same direction

as the outer vortex, pressure at the nozzle

converging wall increases and pressure at the swirl

axis decreases.

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Accordingly, as the inner vortex flow

approaches the nozzle, it enters the converging

section of the nozzle, thereby increasing the swirl

or angular velocity and thus producing an

enhanced radial pressure gradient that blocks the

outflow of the fresh incoming stream .The above-

described flow field has several unique

characteristics. First, the flow path of the injected

fluid before reaching the outlet is quite long and

highly convoluted. Thus, it provides an

opportunity for intense and extensive mixing

along the flow path, particularly in the core or

inner vortex where the angular velocity of the

swirl is greater. Secondly, the outer and inner

vortexes are individually discrete. Thus, the fluid

flow in the inner vortex does not mix significantly

with the fluid flow in the outer vortex.

This enables the inner vortex to support

burning or other chemical reactions to some

significant degree independent of the outer vortex.

Because of this, materials such as propellant or

other chemicals, can be added to the inner vortex

by injection at the conjunction of the two vortices

at the closed end of the chamber and cause

combustion or other chemical reaction to occur and

be sustained wholly in the inner vortex if so

desired The ability to produce and sustain the

above-described double vortex field flow has

countless potential application and several

immediate practical applications.

Object of the present invention is to provide a

hybrid propulsion system that inherently cools the

case walls whenever fuel is not present to insulate

the wall from hot combustion products. A more

specific object of the present invention is to

provide a hybrid rocket propulsion system that

creates and uses a unique internal combustion

vortex flow field to enhance grain regression rate

and to increase the efficiency of the combustion

process. Another object of the present invention is

to provide a combusting flow field that allows the

use of a single grain port for the combustion

process. A further object of the present invention is

to provide an injection means for the fluid

propellant that induces the double vortex flow

field in the grain combustion port. A further object

of the present invention is to provide a combustion

process that inhibits combustion instability.

Another object of the present invention is to

provide a double helix flow field in which an outer

helix flows upwards along the grain surface

inducing combustion, and an inner combustion

helix flows down the port centerline and out the

nozzle to produce thrust.

To achieve the foregoing and other objects and in

accordance with the purpose of the present

invention, a self- contained propulsion system is

provided with a motor casing that houses a solid

propellant grain. A first fluid propellant that will

combust when in the presence of the solid

propellant in the presence of an ignition source, is

stored separately from the solid propellant in a

fluid tank. A delivery means supplies at least a

portion of the said fluid propellant in either liquid

or gaseous state to the combustion port of the solid

grain. An ignition means initiate’s combustion

with the combustion port of the solid propellant

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grain. A fluid injection means that will cause the

fluid propellant to enter the solid propellant grain

case in such a manner as to form an up flowing

helix along the surface of the combustion port in

the solid propellant grain and then a down flowing

helix along the centerline of the combustion port,

said down flowing helix to eventually exit the

chamber via the discharge nozzle.

The fluid propellant can be provided to

the entrance to the fuel grain case by any of

various common means, including delivery from

pressurized tanks, or by pumps of suitable designs.

The fluid can be either the liquid or gaseous state.

Commonly the fluid propellant is the oxidant. In

one embodiment, the oxidant is burned in a highly

oxidizer-rich combustor (termed a "pre-burner")

and the resulting oxidizer-rich combustion

products are used to drive a turbo pump that

pressurizes the liquid oxidizer for delivery to the

pre-burner. After driving the turbine, the oxidizer-

rich combustion products leave the turbine and

flow to the injection ports of the fuel grain high

pressure casing.

The oxidant enters the fuel grain ports in a

fluid phase that may be at high enough pressure to

be supercritical. The injector elements are

positioned and designed such that the injected

flow develops the co-axial vortex flow field within

the chamber in the manner that is the subject of

this invention. In another embodiment, the

oxidizer in liquid state is carried in a high pressure

tank. Pressure is supplied by a conventional tank

pressurization system well known to those

acquainted with the profession. The liquid oxidant

is expelled from the tank and delivered at high

pressure to the injection ports of the fuel grain high

pressure casing.

2.1 Combustion Chamber

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Figure 2; Dimensions of combustion chamber.

This is the bottom view of the combustion

chamber .diameter for each holes are shown in the

diagram itself. All dimensions are in mm.

2.2 Fuel Injector

Figure 3; Fuel injector

This is the figure of the fuel injector where

fuel is injected into the combustion chamber. It

consists of small minute holes in order to get

maximum atomization of the fuel. The holes are

inclined in such a way that it enables the fuel to

coincide at the center ,which help to strike the fuel

coming from each holes at center and splash it to

get the maximum atomization.

Solid Works Flow Simulation uses Computational

Fluid Dynamics (CFD) analysis to enable quick,

efficient simulation of fluid flow and heat transfer.

Inlet mass flow rate of fuel is 0.3 lb/sec, which is

indicated on the top portion of the combustion

chamber, inlet mass flow rate of the oxidizer is

0.547lb/sec and the outlet environment pressure is

101325 Pascal.

3 RESULT

First, the high velocity outer vortex scrubs

the burning fuel grain surface, causing enhanced

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heat transfer to the surface. Combustion near and

on the surface is also able process because fresh

oxidizer is carried directly to the surface by

turbulent transport mechanisms in addition to the

usual molecular diffusion process. Second, the

vortex also sustains radial pressure and density

gradients that cause hot, low density combustion

products to be buoyed out of the combustion zone

so their presence does not hinder the combustion

process. Third, because the flow path of the

injected fluid (the oxidizer) to reach the outlet is

very long and highly convoluted, it provides an

opportunity for intense and extensive mixing and

combustion with the fuel grain vapor, particularly

in the core or inner vortex. Accordingly, in the

above application, the outer vortex flow causes

rapid burning of the fuel grain on the wall of the

cylinder, and the inner vortex causes combustion

to proceed rapidly, by providing intense mixing

and combustion travel distance to allow

combustion to reach completion, thereby achieving

high combustion efficiency.

3.1 Visualizing Results

After running the analysis, the software

generates customizable default result plots.

Other plots can also be defined by right-

clicking a result folder and selecting Define. When

defining plots, you can use reference coordinate

systems. For example, you can view radial and

tangential stresses by selecting an axis when

defining stress plots. You can associate result plots

with named views.

Result viewing tools include fringe plots,

section plots, iso plots, animation, probing, and

exploded views. For sections plots, you can choose

planar, cylindrical, and/or spherical cutting tools.

A clipping utility is provided for convenient

viewing of section and iso plots.

Solid Works Flow Simulation provides advanced

easy-to use tools to visualize the results: Cut, 3D-

Profile and Surface Plots (contours, isolines, and

vectors), Isosurfaces, XY plots, Flow and Particle

Trajectories, Animation of Results. Solid Works

Flow Simulation provides advanced tools to

process the results: Point, Surface and Volume

Parameters, Plots of Goals, MS Word Report.

This figure below shows the temperature

distribution inside the combustion chamber. The

temperature is varied at each place in the

combustion chamber. From the figure it is clear

that the temperature at the wall of the combustion

chamber is considerably low. High temperature is

obtained at the core portion as well as at the top of

the combustion chamber. The table at the left side

of the figure shows the variation of temperature

along the combustion chamber. Near the wall of

the combustion chamber a very low temperature is

developed, which is seen in green color in the

figure.

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Figure 4: temperature distribution inside the

combustion

The high intense temperature is at the

core, which has red color. When the flow comes to

exit its temperature is considerably low and having

a color of blue. From this figure we can understand

that the wall of the combustion chamber is

protected from developing a high temperature by

the swirl shield effect. So here the prevention of

generating heat in the combustion chamber wall is

done rather than curing it after the heat generation.

The temperature value of each color is indicated in

the left side table.

Figure 5: velocity distribution inside the combustion

In the above figure, the velocity distribution of

oxidizer flow inside the combustion chamber .The

corresponding values of velocity for different

colors is shown in the left side table. The velocity

of oxidizer at the outer vortex is different from that

of inner vortex. The outer and inner vortexes are

represented in sky-blue and dark blue color

respectively. At the throat region velocity is

reaches to match velocity, which can be identified

by the color and velocity value combination from

the table. Because of the convergent divergent

nozzle the velocity of flow after the throat is

supersonic; this is represented by the red color

flow lines. The arrow marks on each flow line

shows its direction.

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Figure 6: temperature distribution inside the

combustion

This figure shows the temperature

distribution of the gas flow lines, inside the

combustion chamber. The temperature is reduced

when it goes from top to bottom and also towards

the core region from the periphery. The intensity of

temperature is increased from the blue color to red

color, which is shown in the left table. The arrow

mark on each flow line indicates its direction.

3.2Experimentaltest

At the time of ignition

After 5 seconds

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After 15 seconds

after 30 seconds

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4 CONCLUSION

The present invention relates generally to a vortex

flow field and the apparatus and method to

produce and sustain it and more particularly to a

hybrid rocket engine and a method of propelling a

rocket utilizing such vortex flow field. The flow

field in accordance with the present invention is

capable of providing separate regions or zones

within and among one or more flowing fluids

contained within a common chamber, without the

need for diaphragms or other physical separators

or barriers. It is evident and believed that the flow

field of the present invention has utility to a wide

range of applications. One general field of

application is that of combustion chambers, and

more particularly, that of combustion chambers

and methods for rocket engines or the like and

hybrid rocket propulsion systems. A combustion

chamber and method in accordance with one

embodiment of the present invention utilizes the

unique flow field of the present invention to

improve hybrid rocket fuel regression and increase

mixing length in a rocket or other engine. Another

embodiment is in the form of liquid rocket engine

to prevent hot combustion products from

contacting the chamber wall. By this new

innovative idea we developed a new rocket engine

which has 20% weight reduction than the

conventional rocket engine. This is accomplished

by avoiding the extra cooling mechanism that is

used in conventional engines. Here we prevent the

formation of heat on the wall of the combustion

chamber rather than cooling it after it become hot.

ACKNOWLEDGMENT

I gratefully remembers the contribution made by

Sarin Jose, Rohan Paulose, Leo kJ 2013 batch

students of VJECfor their contribution in this

project and for giving me the permission to present

the paper. Also humbly acknowledges the

contribution of Prof. Jerin Cyriac, the professor of

mechanical engineering, at Vimal Jyothi

engineering college, Chemperi, for the great

contribution he had done to this project and also

for guiding me from the beginning to the end.

REFERANCE

1. 1. Aerospace Propulsion, by Dennis G. Shepherd,

Elsevier Publishing Company, 335 Vanderbilt Avenue,

New York, NY, 1972 . ISBN 71-190302.

2. 2 Rocket Propulsion Elements, by George P. Sutton.

John Wiley & Sons, Inc., New York, 1964.

3. 3 Design of Liquid, Solid, and Hybrid Rockets, by R. L.

Peters. Hayden Book Co. Inc., New York, 1965.

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Abstract- Index Terms IJSER...tangential injection causes the flow in the chamber to swirl and...

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